Mid-infrared surface plasmon resonance in zinc oxide semiconductor thin films

Surface plasmon resonance (SPR) in semiconducting materials at mid-infrared (mid-IR) energies offers the potential for new plasmonic functionalities and integration schemes. Mainstream semiconductors are transparent to mid-IR energies, thus a tightly integrated monolithic package for SPR sensing becomes feasible. We report mid-IR surface plasmon resonance in zinc oxide as a model material for semiconductors with 4 × 10¹⁹ to 8 × 10 ¹⁹ cm^-3 carriers. The surface plasmon modes were characterized using spectroscopic IR-ellipsometry and compared to a reflectivity simulation. The data confirm the feasibility of mid-IR SPR, show a generic ability for plasmon tuning, and demonstrate the predictive power of the reflectivity model.